Theoretical Synthesis Core Brief Abstract The Theoretical Synthesis Core will serve as a resource to the Center, practitioners, and the international research community in terms of theoretical integration, training and development. We will provide interdisciplinary-theory-based training and consultation to CDUHR staff who are developing research proposals, analyzing data, writing papers and reports, or preparing intervention or policy plans. We will work to develop new and useful ways to theorize processes and causal relationships within and across disciplines (including the fields of social sciences, behavioral research, epidemiology, infectious diseases, medicine and viral evolution) and levels of analysis that will help us understand and intervene in the epidemics of HIV and other infectious diseases among drug users and their communities. As we develop such theories, and as we become aware of useful theoretical developments elsewhere in the field, we will disseminate them within CDUHR and to local, national and international practitioners, affected populations, researchers and policy makers.